Biodegradable and Reusable Cellulose-Based Nanofiber Membrane Preparation for Mask Filter by Electrospinning

Environmentally friendly face masks with high filtration efficiency are in urgent need to fight against the COVID-19 pandemic, as well as other airborne viruses, bacteria and particulate matters. In this study, coaxial electrospinning was employed to fabricate a lithium chloride enhanced cellulose acetate/thermoplastic polyurethanes (CA/TPU-LiCl) face mask nanofiber filtration membrane, which was biodegradable and reusable. The analysis results show that the CA/TPU-LiCl membrane had an excellent filtration performance: when the filtration efficiency reached 99.8%, the pressure drop was only 52 Pa. The membrane also had an outstanding reusability. The filtration performance maintained at 98.2% after 10 test cycles, and an alcohol immersion disinfection treatment showed no effect on its filtration performance. In summary, the CA/TPU-LiCl nanofiber membrane made in this work is a promising biodegradable and reusable filtration material with a wide range of potential applications, including high-performance face mask.

Emerging Developments Regarding Nanocellulose-Based Membrane Filtration Material against Microbes

The wide availability and diversity of dangerous microbes poses a considerable problem for health professionals and in the development of new healthcare products. Numerous studies have been conducted to develop membrane filters that have antibacterial properties to solve this problem. Without proper protective filter equipment, healthcare providers, essential workers, and the general public are exposed to the risk of infection. A combination of nanotechnology and biosorption is expected to offer a new and greener approach to improve the usefulness of polysaccharides as an advanced membrane filtration material. Nanocellulose is among the emerging materials of this century and several studies have proven its use in filtering microbes. Its high specific surface area enables the adsorption of various microbial species, and its innate porosity can separate various molecules and retain microbial objects. Besides this, the presence of an abundant OH groups in nanocellulose grants its unique surface modification, which can increase its filtration efficiency through the formation of affinity interactions toward microbes. In this review, an update of the most relevant uses of nanocellulose as a new class of membrane filters against microbes is outlined. Key advancements in surface modifications of nanocellulose to enhance its rejection mechanism are also critically discussed. To the best of our knowledge, this is the first review focusing on the development of nanocellulose as a membrane filter against microbes.

The deposition of nanofibers onto a traditional filtration medium and their effects on filtration efficiency

Traditional filtration media composed of fibers with sizes on the micrometer scale have difficulty filtering particles a little smaller than 300 nm. Even though nanofibrous materials are able to capture these particles and can have excellent filtration efficiency, their widespread use continues to be inhibited by several obstacles, particularly an excessive pressure drop and the inability to form self-supporting filtration membranes. We have prepared two types of composite materials, namely an ultra-thin nanofibrous layer made of polyurethane or nylon with various fiber diameters and pore areas. Scanning electron microscopy was used for their characterization. The nanofibrous layer was deposited directly onto a traditional melt-blown polypropylene filtration fabric with a very low area weight of 30 g/m2, which facilitates handling and bypasses the need for the layer to be self-supporting. Moreover, a fine polyethylene mesh was added as a separate layer to prevent humidity from passing through the filtration material as well as to cover fabrics. The filtration efficiency and the pressure drop of the prepared materials were determined. The results showed that the incorporation of a nylon nanofibrous layer with smaller fiber diameters and pore areas leads to a significant increase in the filtration efficiency (92%) against the most penetrating particles, the critical size of which decreased to 50 nm, while the pressure drop was comparable to the pressure drop of a commercially available FFP2 respirator. The prepared filtration material could be used to manufacture respirators.

Cationic Nanocellulose as Promising Candidate for Filtration Material of COVID-19: A Perspective

The threat of the novel coronavirus (COVID-19) pandemic is worrying as millions of people suffered from this outbreak. The COVID-19 can be airborne by attaching to human nasal or saliva secretion of an infected person or suspended fine particulates in the air. Therefore, in order to minimize the risks associated with this pandemic, an efficient, robust and affordable air‐borne virus removal filters are highly demanded for prevention of spreading viruses in hospitals, transportation hubs, schools, and/or other venues with high human turn‐over. Respirators such as N95, N99 and N100 as well as surgical masks have been widely used. To date, there is no filter standards or special filter technologies tailored for effectively adsorbing the airborne viruses. Studies had shown the electrostatic fibers were capable to entrap the negatively charged viruses including COVID-19. Researchers believed that the positive surface charge of filtration material is an important key to efficiently adsorb the negatively charged viruses. Nanocellulose has emerged as a new class of biobased material with promising potential application in the filtration of viruses. Nanocellulose which is uniform in diameter and has excellent nanofibrillar morphology. To the best of our knowledge, lack of study is done to determine the efficiency of cationic nanocellulose as filtration material of COVID-19.

Emerging Developments Regarding Nanocellulose-based Membrane Filtration Material Against Microbes

Wide availability and diversity of dangerous microbes poses a considerable problem for health professionals and in the development of new healthcare products. Numerous studies have been conducted to develop membrane filters that have antibacterial properties to solve this problem. Without proper protective filter equipment, healthcare providers, essential workers, and the general public are exposed to the risk of infection. A combination of nanotechnology and biosorption is expected to offer a new and greener approach to improve the usefulness of polysaccharides as an advanced membrane filtration material. Nanocellulose is among the emerging materials of this century and several studies had proven its usefulness in filtering microbes. Its high specific surface area enables the adsorption of various microbial species, and its innate porosity can separate various molecules and retain microbial objects. Besides that, the presence of an abundant OH groups in nanocellulose allows its surface modification which can increase its filtration efficiency through the formation of affinity interactions toward microbes. In this review, an update of the most relevant uses of nanocellulose as a new class of membrane filters against microbes is outlined. Key advancements in surface modifications of nanocellulose to enhance its rejection mechanism is also critically discussed. To the best of our knowledge, this is the first review focusing on the development of nanocellulose as a membrane filter against microbes.

Nitrogen and Phosphorus Accumulation in Horizontal Subsurface Flow Constructed Wetland

The article presents the results of studies aimed at determining the level of accumulation of total nitrogen and total phosphorus in parts of reeds (Phragmites australis (Cav.) Trin. ex Steud.), as well as in a constructed wetland bed. The influence of the vegetative phase and dormancy of plants on the level of accumulation of biogenes in plant parts and in the bed of constructed wetland was investigated. Young plants at the stage of intensive growth were found to contain the most total nitrogen and total phosphorus. The leaves of the common reed, on the other hand, revealed the highest ability for the phytoaccumulation of nitrogen (32.21 gN/kg d.m.). Accumulation of total phosphorus in the leaves of reeds was, on average 1.54 gP/kg d.m. The results of studies on the filtration material filling the beds showed that the surface layer of up to 20 cm in depth was characterized by the highest total nitrogen content and total phosphorus content (average: 12.53 gN/kg d.m. and 3.01 gP/kg d.m.). The accumulation of these compounds decreased along with the depth of the deposit as well as in the direction of the outflow of sewage from the constructed wetland.

Antibacterial Capability of Triclosan Treated on Filter Fiber Materials

Antibacterial filtration material is an effectively control technique of airborne biological pollutant to purify indoor air. This study aims to assess the antibacterial capability of triclosan treated on three filter fiber materials: the glass fiber (GF), the non-woven fabric (NF) and the chemical fiber (CF). Triclosan was loaded on filtration materials by the impregnation method. E. coli, S. albus and S. aureus were used as test strains. It’s found that the filter materials loaded with triclosan showed obvious antibacterial zone: the antibacterial zones against E. coli were 11.5 mm(GF), 13.2 mm(NF) and 11.0 mm(CF) respectively; zones against S. albus were 28.0 mm(GF), 21.0 mm(NF) and 25.0 mm(CF); zones against S. aureus were 21.5 mm(GF), 14.0 mm(NF) and 11.5 mm(CF). The percent reduction of bacteria of antibacterial fiber treated with triclosan against E. coli were 78.57% (CF) and 80.00% (GF), the percent reduction of bacteria of triclosan treated fiber against S. albus were 68.59% (NF) and 82.52% (CF), respectively. This research provided an effective antibacterial filter fiber material loaded with triclosan and it aids to reduce the transmission and harm of infectious diseases and to decontaminate the indoor environment.

Nanocellulose-Based Filters as Novel Barrier Systems for Chemical Warfare Agents

Current world events have made several countries as a target for terrorism. Chemical weapon such as nuclear weapon is commonly referred as a weapon of mass destruction. Organophosphorus (OP) compounds have long been used as pesticides and developed into warfare nerve agents such as tabun, soman, sarin, and VX. They are highly toxic and considered to be the most dangerous chemical weapons. Development on the protection material against OP compounds has gained interest among researcher. Nanocellulose has shown a great potential for high-performance filtration material due to its interesting characteristics such as high adsorption capacity, large surface area, high strength, renewable, chemical inertness, and versatile surface chemistry. Therefore, the evaluation of the chemical interaction between nanocellulose and organophosphorus is important. The analyses of fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-Vis), and elemental analysis were carried out in this study. It was found that the nanocellulose is capable to adsorb OP compound by forming the hydrogen bonding. The adsorption rate was increased as the nanocellulose concentration increased. This is the initial step to discover the potential of nanocellulose to be used in military protection mask.